The present invention relates to transfer components, and more specifically, to intermediate transfer components useful in transferring a developed image in an electrostatographic, including xerographic and digital, machine, from a photoreceptor or another transfer member to a copy substrate or another transfer member. In embodiments of the present invention, there are selected transfer components comprising a layer comprising electrically conductive fillers of polyanaline and carbon black. Also, in embodiments, the transfer member comprises a polyimide substrate. The present invention, in embodiments, allows for the preparation and manufacture of transfer components with resistivity within the desired range for transfer, resulting in excellent electrical properties against a wide variations in transfer fields and enabling the transfer members to be useful at a wide variety of process speeds. The present invention, in embodiments, also allows for a decrease or elimination in pre-transfer air breakdown of the transfer member.
In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles which are commonly referred to as toner. Generally, the electrostatic latent image is developed by bringing a developer mixture into contact therewith. A dry developer mixture usually comprises carrier granules having toner particles adhering triboelectrically thereto. Toner particles are attracted from the carrier granules to the latent image forming a toner powder image thereon. Alternatively, a liquid developer material may be employed. The liquid developer material includes a liquid carrier having toner particles dispersed therein. The liquid developer material is advanced into contact with the electrostatic latent image and the toner particles are deposited thereon in image configuration. After the toner particles have been deposited on the photoconductive surface, in image configuration, they are transferred to a copy sheet. However, when a liquid developer material is employed, the copy sheet is wet with both the toner particles and the liquid carrier. Thus, it is necessary to remove the liquid carrier from the copy sheet. This may be accomplished by drying the copy sheet prior to fusing of the toner image, or relying upon the fusing process to permanently fuse the toner particles to the copy sheet as well as vaporizing the liquid carrier adhering thereto. However, it is desirable to refrain from transferring any liquid carrier to the copy sheet. Therefore, it is advantageous to transfer the developed image to an intermediate transfer component, and subsequently transfer with very high transfer efficiency, the developed image from the intermediate transfer component to a permanent substrate. The toner image is usually fixed or fused upon a support which may be the photosensitive member itself or other support sheet such as plain paper.
In an alternative reproducing apparatus, marking material may be deposited image-wise onto a first image-bearing member. This marking material is then transferred onto a second image-bearing apparatus such as an intermediate transfer member in accordance with an embodiment of this invention. Subsequently, the marking material may be transferred onto a third image-bearing member, typically the final copy sheet, such as paper, transparency, or the like. The marking material of this alternative reproducing apparatus may include a waxy material that is melted and projected onto the first image bearing member, dry toner particles that are electrostatically or acoustically projected onto the first image bearing member, or liquid toner that is partially dried as it is projected from an orifice to the first image bearing member. The marking material may be charged before, during, or after its deposition onto the first image bearing apparatus. The transfers to the second and third image bearing members may use electric fields, differential adhesion and/or the like. This invention provides controlled resistivity for the second image-bearing member and this controlled resistivity is especially beneficial in electric field induced transfer.
U.S. Pat. No. 5,298,956 to Mammino et al. discloses a seamless intermediate transfer member. Polyimide is listed as a possible layer for the intermediate transfer member. A polymer filler such as polyanaline is also disclosed.
U.S. Pat. No. 5,876,636 to Schlueter, Jr. et al. discloses haloelastomer and doped metal oxide compositions. The compositions are disclosed as being useful as layers in xerographic components. Polyanaline and carbon black fillers are given as examples of conductive fillers.
U.S. Pat. No. 5,995,796 to Schlueter, Jr. et al. discloses haloelastomer and doped metal oxide film components useful in xerographic processes. Polyanaline and carbon black fillers are given as examples of conductive fillers.
In scalable tandem color marking, charged toner particles are transferred first to an intermediate transfer belt and then to a final substrate. Some transfers use electric fields to transfer the toner particles. In other machines, the first transfer is electrostatic and the second transfer can combine transfer and fixing. For a given applied voltage, for example on a bias transfer member, the electrical resistivity of an intermediate transfer member determines the voltage drop across the intermediate transfer member and the field acting on the toner particles. A small range of resistivity is desired to give the high transfer fields without pre-transfer air breakdown. It is difficult to manufacture a material transfer layer having this narrow resistivity.
Attempts at achieving this narrow resistivity have led to loading an elastomer transfer substrate with conducting particles. However, this loading typically leads to a large decrease in resistivity when the loading reaches a value called a percolation threshold. The rapid change of resistivity near the percolation threshold makes it difficult to reproducibly manufacture material with the desired resistivity. Small changes in particle concentration, in particle morphology, in particle surface chemistry, or in particle aggregation into larger aggregates, cause large changes in resistivity.
A very conductive intermediate transfer member is not desirable because the high transfer fields cause arcing at the charge deficient spots on the photoconductor. In addition, a very conductive intermediate transfer member results in high pre-transfer fields that cause air breakdown and toner discharge prior to transfer. Conversely, a very insulating intermediate transfer member is not desirable because the result is a large voltage drop across the intermediate transfer member and only a weak field to transfer toner.
Therefore, it is desirable to provide an intermediate transfer member that has a volume resistivity within a desired range necessary for sufficient transfer of toner within a wide variety of process speeds. It is further desirable to provide an intermediate transfer member that possesses a wide latitude against variations in the transfer field.
Attempts at making such a semi-insulating intermediate transfer member having the above desired characteristics have been difficult. Attempts focused on using an insulating plastic or elastomer loaded with conducting particles or with ionic conductors. Control of volume resistivity by loading with ionic conductors is difficult because changes in relative humidity generally lead to changes in resistivity. Sometimes this occurs as soon as the relative humidity changes and sometimes it occurs only after prolonged printing at an extreme corner of the print engine""s environmental window (i.e., the range of temperatures and humidities at which the print engine operates).
Therefore, there is still a need for a semi-insulating intermediate transfer member which can be used for transferring a toner image across a wide variety of process speeds, and that possesses a wide latitude against variations in the transfer field.
Embodiments of the present invention include: a transfer member having a substrate comprising a polyimide having polyanaline and carbon black electrically conductive fillers dispersed therein.
In addition, embodiments include: an image forming apparatus for forming images on a recording medium comprising: a charge-retentive surface to receive an electrostatic latent image thereon; a development component to apply toner to the charge-retentive surface to develop the electrostatic latent image to form a developed image on the charge retentive surface; a transfer component to transfer the developed image from the charge retentive surface to a copy substrate, the transfer member having a substrate comprising a polyimide having polyanaline and carbon black electrically conductive fillers dispersed in the substrate.
Moreover, embodiments include: a transfer member comprising a substrate comprising a polyimide having from about 5 to about 25 percent by weight of total solids polyanaline, and from about 1 to about 10 percent by weight of total solids carbon black electrically conductive fillers dispersed therein, wherein the transfer member has an electrical volume resistivity of from about 107 to about 1013 ohm-cm.